For chocolate glaze, combine sugar, cocoa, cornstarch and water in large microwavable bowl; whisk until smooth. Microwave on HIGH 4 to 6 minutes, stirring every 2 minutes, until slightly thickened. Stir in vanilla.

To serve, for each dessert drizzle 2 tablespoons chocolate glaze onto plate. Cut 1 cupcake in half; place halves on top of glaze. Top with about 2 heaping tablespoonfuls pudding. Garnish as desired. Serve immediately.